Dynamics of organic carbon sedimentation and bottom oxygen and their impact on phosphorus retention in Lake Simcoe: reactive- transport modeling and experimental study.

lovinggudgeonΜηχανική

22 Φεβ 2014 (πριν από 3 χρόνια και 5 μήνες)

59 εμφανίσεις

Goldschmidt 2012 Conference Abstracts


Mineralogical Magazine | www.minersoc.org


Dynamics of organic carbon
sedimentation and bottom oxygen
and
their impact on
phos
p
horus
retention in Lake Simcoe: reactive
-
transport modeling and
experimental study.

M. DITTRICH
1
*
, A. CHESNYUK
1
, J. MCCULLOCH
1
, A.
GUDIMOV
1
, G. ARHONDITSIS
1
, J. YO
U
NG
2
,
J.
WINTER
2
, AND E. STAINSBY
2

1
Department of Physical and Environmental Sciences, University of
Toronto Scarborough, 1265 Military Trail, Toronto, Canada, M1C
1A4, mdittrich@utsc.utoronto.

ca

(* presenting author)

2
Ontario Ministry of the Environment, 125

Resources Road,
Toronto,
Ontario, Canada M9P 3V6, joelle.young@ontario.ca,
jennifer.winter@ontario.ca
,
eleanor.stainsby@ontario.ca

Introduction

Lake Simcoe
experiences

cultural eutrophication
associated with
point and non
-
point loading sources
. Efforts to

reduce total
phosphorus (P)

inputs to Lake Simcoe

since the 1990s, have resulted
in significant annual load

reductions to the lake
[1]
.
T
his lake still
suffers from excessive growth of filamentous alga
e
, macrophyte
s
,
and low hypolymnetic oxygen concentrat
ion. Despite a good
understanding of the total
P

budget, our knowledge about the
potential for bioavailable P loadin
g from the sediments is limited
.
The impact of d
ynamic conditions at sediment

water interface, such
as organic carbon flux and oxygen conc
entration, on phosphorus
retention remains unknown
.
In this study, phosphorus sediment
retention in three basins, that experienced distinct sedimentation
dynamics, has been investigated experimentally and theoretically.
Using diagenetic reaction
-
transport
modeling and sediment core
analysis, we investigated the effects that variations in the organic
carbon loadings and oxygen bottom concentration, had on the
availability of sediment P.

Methods and Results

We performed phosphorus sequential fractionations o
f sediments
during
summer stratification and under ice
-
cover. Phosphorus
binding forms have been divided into four operational groups:
apatite
-
bound
-
P
, organic
P
, inorganic
redox
-
sensitive P

(
iron
-
hydro
-
oxides
-
bounded
) and
loosely
-
bound P, that is in equil
ibrium with

P
dissolved in pore water.

The following rank was determined for the P in the sediment
apatite
-
P

>
organic
-
P

>

redox
-
sensitive
-
P

>

loosely bound
-
P. It was
found that the largest amount of P is bound in the sediment as
apatite
-
P
, essentially
st
able in respect to redox conditions
.
The model
results
are
in agreement with the measured flux of total phosphate to
the system and the fractionation data of phosphorus binding forms. A
sensitivity analysis was undertaken to identify the most significant
p
arameters, demonstrating that variations in sedimentation rate, and
bottom water oxygen concentration, have the largest impact

on P
diagenesis
.

[1]
Hiriart
-
Baer

et al.
(
2011
)
Temporal trends in phosphorus and
lacustrine productivity in Lake Simcoe inferre
d

from lake sediment
,
Journal of Great Lake Research,
37
, 764
-
771
.